Petroleum is an indispensable source for energy and chemicals. At the same time, petroleum and petroleum based products are also a major source for air and water pollution. To address growing concerns with pollution caused by petroleum and petroleum based products, many countries have implemented strict regulations on petroleum products, particularly on petroleum refining operations and the allowable concentrations of specific pollutants in fuels, such as, sulfur content in gasoline fuels. For example, motor gasoline fuel is regulated in the United States to have a maximum total sulfur content of less than 10 ppm sulfur.
As noted above, due to its importance in our everyday lives, demand for petroleum is constantly increasing and regulations imposed on petroleum and petroleum based products are becoming stricter. The available petroleum sources currently being refined and used throughout the world, such as, crude oil and coal, contain much higher quantities of impurities (for example, elemental sulfur and compounds containing sulfur, nitrogen and metals). Additionally, current petroleum sources typically include large amounts of heavy hydrocarbon molecules, which must then be converted to lighter hydrocarbon molecules through expensive processes like hydrocracking for eventual use as a transportation fuel.
Current conventional techniques for petroleum upgrading include hydrogenative methods using hydrogen in the presence of a catalyst, in methods such as hydrotreating and hydrocracking. Thermal methods performed in the absence of hydrogen are also known, such as coking and visbreaking.
Conventional methods for petroleum upgrading suffer from various limitations and drawbacks. For example, hydrogenative methods typically require large amount of hydrogen gas from an external source to attain desired upgrading and conversion. These methods also typically suffer from premature or rapid deactivation of catalyst, as is typically seen with heavy feedstock and/or harsh conditions, thus requiring the regeneration of the catalyst and/or addition of new catalyst, thus leading to process unit downtime. Thermal methods frequently suffer from the production of large amounts of coke as a byproduct and the limited ability to remove impurities, such as, sulfur and nitrogen. This in turn results in the production of large amount of olefins and diolefins, which may require stabilization. Additionally, thermal methods require specialized equipment suitable for severe conditions (high temperature and high pressure), require an external hydrogen source, and require the input of significant energy, thereby resulting in increased complexity and cost.